The idea
Divisibility rules test whether a number divides exactly without a remainder.
Follow these steps
- Choose the rule for each required divisor.
- Test every condition against the whole number.
- Confirm that all required rules hold, not just one.
See the method in action
Example 1
Which number is divisible by 5?
- A whole number is divisible by 5 when its last digit is 0 or 5.
- Only 135 meets this rule.
Example 2
The candidates are 504, 510, 508, 506, 505. Identify the one number divisible by both 3 and 4, then divide it by 12. What is the quotient?
- The digit sum of 504 is 9, a multiple of 3, and its final two digits, 04, form a multiple of 4.
- The other candidates fail at least one test.
- Finally, 504 ÷ 12 = 42.
A useful shortcut
Confirm that all required rules hold, not just one.
Watch out for these
Three fresh questions
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